In the past, in a transmission apparatus, plug-in units and a motherboard that controls the relevant plug-in units have been coupled to each other via a shared signal line such as, for example, a bus line, which is used in common by the plug-in units. The shared signal line is branched within the motherboard and is coupled to the plug-in units.
As for a noise generated in such a shared signal line, there has been proposed a method for measuring the number of times a noise greater than or equal to a predetermined level and included in an output of a synchronization separation unit is generated while a generated mask pulse is active (see, for example, Japanese Laid-open Patent Publication No. 7-162898).
There has been proposed an apparatus that suppresses a noise at a track jump position within a measured jitter by generating a mask pulse set to a predetermined duration and triggered by a generated delayed pulse (see, for example, Japanese Laid-open Patent Publication No. 2007-115355).
There has been proposed an apparatus that does not perform binarization in a portion of a signal component, the portion being likely to be buried in a noise component, in a tracking error signal generation circuit related to an optical disk recording medium (see, for example, Japanese Laid-open Patent Publication No. 2006-053968).
In such a configuration as described above, a reflection noise in a shared signal line fluctuates depending on states (the number of connections, or connection points) of mounted plug-in units. As a result, depending on connection states of the mounted plug-in units, the length of an undefined time period during which a level of a signal is unstable and a logic level is not confirmed changes. Therefore, in a transmission apparatus, a worst case of a maximum undefined time period is assumed, and control tailored to the undefined time period in the worst case is performed. Therefore, there is a problem that the transmission rate of a signal transmitted through the shared signal line is uniformly suppressed to a low level regardless of connection states of the plug-in units. From the above, it is desirable to be able to optimize, in conformity with the connection states of the plug-in units, the transmission rate of a signal transmitted through the shared signal line.